1. Field
Example embodiments relate to an alignment method for performing an overlay using a virtual mask in a maskless exposure process.
2. Description of the Related Art
Generally, a method of forming a pattern on a substrate (or a semiconductor wafer) contained in a Liquid Crystal Display (LCD), a Plasma Display Panel (PDP), a Flat Panel Display (FPD) may include the following. First, a pattern material is deposited over a substrate, and is selectively exposed using a photomask, such that a specific pattern material part having a changed chemical property or the remaining parts other than the specific pattern material part is selectively removed, thereby forming a pattern.
However, as the size of substrate is gradually increased and the precision of pattern is also gradually increased, a maskless exposure process of forming a desired pattern on the substrate (or semiconductor wafer) without using a photomask has been recently developed. The maskless exposure technique may not include costs associated with manufacturing/cleaning/keeping a mask, may freely design a panel, and does not require a mask manufacturing time, resulting in a reduction in lead time. Since there is no mask defect, there is no damage in a fabrication process. Because a hybrid layout is used, the production flexibility is increased.
A plurality of layers is deposited over a substrate, such that they form a pattern over the substrate through an exposure process. The higher the precision of pattern, the higher the number of layers each having the pattern. When a plurality of layers is deposited over one substrate, a conventional mask exposure method is designed to arrange the layers using alignment marks of a mask and a substrate (or wafer).
However, since a mask is not present in the maskless exposure, it may not be possible to recognize a relative position between alignment marks of a mask and a substrate.